Throughout the life of an oil and gas field, the extraction and injection of fluids results in changes in the in situ stress and physical properties of the reservoir. Microseismicity and surface heave/subsidence are among the common responses to these injection- and production-induced stress perturbations.
A passive seismic survey relies upon passive seismology, e.g., seismology that does not rely upon the use of a controlled seismic source of energy for sending sound waves into the earth at predetermined locations, such as dynamite, air guns and/or vibrators. In contrast to active seismic surveys, passive seismic surveys typically rely upon natural or induced teleseismic events and/or microseismic activity that may be recorded at one or more recording location(s). In the case of injection- and production-induced stress perturbations, a successful passive seismic survey requires a determination of when the induced stress change is expected to be large enough to generate microearthquakes. The expected magnitude and recurrence rate of these events should also be determined. The detection capability of a specific seismic array should be determined, and it should be determined if the microseismic signal amplitudes are large enough to be detected in a noisy environment.
The present inventors have developed one or more techniques that utilize coupled geomechanical-reservoir simulation that can handle complex 3-D geologic structures and reservoir pressure variations during production to quantify the presence, timing, location, and magnitude of microseismicity in and around the reservoir. The integration of geomechanical modeling with seismic modeling permits an accurate calculation of the probability of detection of seismic events given an acquisition network in the area.